I would the do the IP timing before you check the Pre-chambers.
There is a guy on Ebay that sells the drip tubes that he makes from used Fuel Injector Lines. Take a look at the picture of his and you will see what yours should look like.
Also replacing the Pre-chambers requires some special tools so Pre-chambers are not a routine removal item.
What I am wondering about is if there is 60 thousnd miles on an overhauled engine why the Valve Stem Seals would be shot; were the OEM seals or after market seals.

__________________
84 300D, 82 Volvo 244Gl Diesel